Use custom KMS store implementation instead of Aries storage provider

[DRK3]

With this change in Aries, a consumer of the Aries KMS interface can now inject in their own storage without being limited by the overall Aries storage interface defined in the spi module. For now, I'm using a wrapper as a bridge solution (the kms.NewAriesProviderWrapper call) to allow the KMS project to continue functioning, but in order to reap the benefits of this new storage design we should create our own implementation.